Tubular films are used as sausage casings for processing and packaging sausages, including water or steam cooked sausages. They are also used to process and package various types of deli cuts of meats, such as those made from chicken, beef, and ham. One particularly typical film is made from regenerated cellulose, where viscose is extruded through an annular die into a coagulating and regenerating bath to produce a tube of regenerated cellulose, as is well-known in the art. This tube is subsequently washed, plasticized, e.g., with glycerin, and can be impregnated with a water-soluble, casing-permeable flavorant or colorant, and dried while inflated under substantial air pressure. After drying, this cellulose “nonfibrous” casing is wound on reels and subsequently pleated, or “shirred”, on high speed shirring machines. Nonfibrous casings are typically used to process small diameter sausages including polish sausages, wieners, or frankfurters. This type of casing is generally removed from the sausages after processing.
Colorants and/or flavorants are introduced into the interior of the tubing during the manufacturing process, particularly by slugging or spraying. These additives are provided in the casing in order to color and/or flavor the foodstuff processed within. In particular, production of smoked or browned sausages or meats has been accomplished through the use of casings containing liquid smoke or caramel, which transfers to the surface of the encased meat product during processing.
Historically, colorants and flavorants have been applied to various foodstuffs, such as sausage and cheese surfaces, by various means. For example, sausages have been colored and/or flavored by smoking with gaseous or liquid wood smoke; by dipping peeled sausages into a vat containing a colorant; by spraying or dipping encased sausages with a casing-permeable liquid dye and/or flavorant; and by stuffing sausage meat into casings having their interior surfaces coated with a transferable colorant. Use of self-coloring cellulosic casings made with synthetic colorants was approved by the United States Department of Agriculture in 1947 and such casings have been commercially available since 1948. In different regions of the world and for various products, different colors range in popularity and some colorants may impart flavor as well as color.
Various patents disclose coloring or flavor compositions including compositions that contain annatto, norbixin, or bixin. U.S. Pat. No. 5,955,126 discloses the use of a bixin colorant composition wherein the bixin is contained in a water-soluble film-forming agent, and is applied as an internal colorant on shirred casings, providing a red color to sausages processed inside these casings. U.S. Pat. No. 4,877,626 (Ande et al.), which issued in 1989, discloses that a mixture of liquid smoke, caramel, and optionally bixin (or annatto) may be used to directly color and flavor raw meat prior to processing.
Another type of casing, fibrous casing, is made by folding a flat paper or textile so that the opposing side edges overlap, forming a tube, while extruded viscose is applied onto one or both sides of the tube. The viscose impregnates the supporting paper or textile tube and when the viscose coagulates and is regenerated, a fiber-reinforced tube of regenerated cellulose is produced. As with the nonfibrous casing above, flavorings and colorants can be introduced by slugging or spraying them into the interior of the tubing or onto the exterior of the casing. This fibrous casing is generally used in tubular casings having diameters of about 40 mm or more in order to provide dimensional stability, particularly during stuffing with meat emulsion, as in deli meats.
Production of both nonfibrous and fibrous casing is well-known in the art. Fibrous casing are also made with additional outer layers of various materials, such as plastics, to provide desired air and/or water barrier properties. One well-known way to provide barrier protection to the interior of the casing is through the application of liquid polyvinylidene chloride (“PVDC”), which upon drying hardens to a self-sustaining layer that can be removed from the fibrous casing. Examples of these types of casings are found in Chui, U.S. Pat. No. 4,377,187, Smith, U.S. Pat. No. 4,442,868, and Owensby, U.S. Pat. No. 6,296,960. A commercially available fibrous casing of this type is sold by Viskase Companies, Inc., of Darien, Ill., USA, under the name of “MP”.
Another type of casing, thermoplastic casing, is made of multilayered laminated sheets of flat film, which are formed into a tube and sealed closed by various methods, such as by overlapping the ends of the tube and sealing them together using adhesives, or by applying a tape to the edges and sealing it with adhesives or by welding it over the seam with heat. Laminated films are produced by placing layers of various materials, such as nylons, polyethylenes, papers, ethylene vinyl acetates, and ethylene vinyl alcohols, to name a few, adjacent to each other, with or without the use of adhesives, in order to produce films with various desired properties. If the inner layer of the formed tube is an absorbent layer, such as a paper, colorants and/or flavorants can be introduced to this layer. Other such films are described in, for example, U.S. Pat. No. 6,200,613 and Japanese application H2-69131.
Multilayered thermoplastic films also can be made by extrusion lamination where the thermoplastic layer is extruded through a slot die directly onto the adhesive layer, or onto other plastic layers.
An important property of laminated film is that it must not delaminate upon handling or cooking, and in particular, when being peeled off of cooked product. It is extremely disadvantageous to have a layer of paper left on the skin of a cooked sausage as the product is considered unfit for consumption. Also, the film must maintain high strength and low elongation properties. It must be sealable, and the seal must withstand processing conditions. Additional features needed for films that provide flavor or color to the encased food include the ability of the film to absorb adequate amounts of flavoring or coloring material, such as liquid smoke or caramel, and then be able to transfer that material to the encased food product to deliver the specific taste or color. Properties, including water and oxygen barriers, are also desired in order to maintain water levels in the cooked product to minimize weight loss and to keep the product edible if stored with the casing or film left on.
The casings described above are usually provided to the food processor in a “shirred” form. Shining is a method of pleating a long piece of flat casing into a much smaller tube, called a “stick”. For examples, a shirred stick of nonfibrous, small-bored casing that measures about 24 inches in length can contain about 265 feet of casing. Another example is a one-meter long shirred stick of a multilayered laminated casing containing an absorbent inner surface that contains approximately 200 feet of flat casing. These sticks are placed on automatic stuffing machines whereby the sticks are held in place and the foodstuff, in particular sausage emulsions, are introduced under high speed and pressure into the interior of the stick, deshirring the stick and forming the sausages. Larger bore casings are used on machines that encase processed and formed meats, hams, or other whole muscle meats, as well as various deli-type meats. These casings are removed after cooking and the processed meats can be automatically sliced and packaged for sale to the ultimate consumer. Problems with the sticks that cause downtime in manufacturing operations include jamming in the automatic stuffing machines and/or the sticks breaking in the hopper that places the sticks into position on the machine to be stuffed. Also, because of the relatively short length of these deshirred sticks, it would be an improvement to be able to provide much longer lengths of casing to the manufacturer, thereby decreasing downtime of the stuffing machines as they continually replace used-up casing sticks.
Alternatively, flat film is used in automatic sausage manufacture. Currently there are machines available in the market that will take a flat piece of film, slide it over a horn or shoulder that curves the flat film, turns it into a tube, and seals together the two edges of the film with a sealing strip of thermoplastic film, forming a tubular casing. In particular, Poly-Clip System Corp. of Mundelein, Ill., USA, produces these sealing, clipping, and stuffing machines. Patents describing some of these machines can be found in U.S. Pat. No. 7,392,642, U.S. Pat. No. 7,310,926, and U.S. Pat. No. 7,544,118, which are all hereby incorporated by reference. Thermoplastic films such as those made of polyethylenes are particularly used on these machines. As these casings are made, they are stuffed with a meat emulsion, and the products are processed to completion.
The films available for this type of machinery must meet specific manufacturing requirements, including low moisture levels and the ability to withstand the high temperatures needed to weld-seal the casing. The primary benefit of this type of casing is the ability to produce many more sausages per length of film, reducing the downtown due to problems with shirred sticks. Some of these machines can handle 3,000 foot rolls of film before needing to have the film replenished.
Generally, films that contain a flavorant and/or colorant on their absorbent, interior surface have high moisture levels that range from greater than 30% by weight up to about 60% by weight. It is not possible to use these high moisture level-containing films on automatic sealing, clipping, and stuffing machines (“stuffing machines”), as the moisture content interferes with the traction of the film through the machine and causes the film to jam. These films are very tacky, with a high kinetic coefficient of friction, causing them to catch on the shoulder apparatus, preventing the formation of a tube from the flat film. What is needed in the industry is a low-moisture, flavor and/or color-containing, laminated flat film that can be provided in large quantities, thereby substantially increasing the number of foodstuffs that can be made on automatic stuffing machines as compared to those using casing sticks.